DETERMINATION OF SELENIUM SPECIES IN COAL FLY-ASH EXTRACTS

An ion chromatography,method was developed to determine selenite and s elenate in the presence of other common anions in extracts from coal f ly ash samples. The anions were separated using a Dionex AG5 guard col umn and an AS4A separator column and then quantified using conductivit y detection. The eluant consisted of 2.0 mM sodium carbonate and 1.0 m M sodium hydroxide. This method separates selenite and selenate withou t interference problems from nitrate, phosphate, and sulfate. The dete ction limits for selenite and selenate were 0.05 mg/L using a 50-muL s ample injection loop and a detector setting of 1 muS full scale. The s elenium concentrations detected using ion chromatography were compared to total selenium values obtained on the same leachates using inducti vely coupled plasma spectroscopy (ICP) analysis. All the leachates ana lyzed displayed good agreement between IC and ICP values.